Coaxial cable is in widespread use for distributing wideband radio frequency ("RF") information, such as television and radio signals. Coaxial cable typically provides two conductors, a central axial conductor and an outer conductor which is substantially concentric with the inner central conductor. The central conductor is typically completely surrounded by the outer conductor, and a low-loss, high dielectric insulation material, such as plastic foam, separates the two conductors. An outer insulating jacket is usually, although not necessarily, provided over the outer conductor to provide electrical insulation and physical protection to the cable. The outer conductor may be a single element, or it may be a composite of several layered elements of conductive foil, wire braid, etc. One element of a composite outer conductor construction may be a conductive film or coating applied to the outside surface of the low-loss, high dielectric insulation material.
Relatively large diameter, semi-rigid coaxial cables are widely used outdoors in cable television distribution networks as a delivery conduit for delivering the cable network signals to drop box locations near the service subscriber's premises. Smaller, more flexible coaxial cables having external insulating jackets are used to provide service drops to the subscriber premises.
Connectors are provided for connecting the cables in the outdoor environment. Such connectors not only must provide positive, signal-tight electrical connections, they must also provide positive leak-tight, sealed physical connections to prevent intrusion of moisture into the cable. Installation of such connectors typically requires cable end preparation such as coring or removal of the insulator dielectric core for some distance, followed by installation and tightening of the conductor assembly by a trained craftsperson, with or without special tools, depending upon the conductor/cable design. Typically, the outdoor environment connectors provide a central connector element which is secured in coaxial arrangement over an exposed end portion of the central conductor. The central connector element thus contributes significantly to the securement of the connector structure to the prepared cable end.
Usually, the distribution network operator does not want a subscriber to install a connector to a cable for use with "outside plant" distribution boxes, cables and the like; thus, special keyed tools are often provided for use by trained installers in order to preclude unauthorized access to system distribution boxes, service drops and the like.
Within the subscriber premises the opposite situation often exists. Usually, the subscriber has a number of appliances which require interconnection and connection to the service cable outlet jack, typically mounted to and extending outwardly from a wall plate within the home or other interior location, etc. Connections may be needed between the service jack and the jacks of a television set, a video cassette recorder ("VCR"), and a stereo FM receiver, for example.
Small diameter (approximately one quarter inch or smaller), flexible coaxial cables are typically employed to accomplish the needed connections. These coaxial cables typically include a solid wire central conductor, a foam core, an outer composite conductor formed of an inner aluminum coating on the foam core, one or more layers of open-mesh aluminum wire braid and one or more layers of an aluminum foil. The outer composite conductor is typically covered by a plastic outer insulator jacket of one or several layers of insulating material in order to complete the coaxial cable construction. The dimensions of such coaxial cables may vary, depending upon type and source thereof. Also, the properties of the cable may vary, depending on type and source, and also depending upon such factors as ambient temperature. When ambient temperature is low, the polymer cable materials become very stiff and difficult to manouver during connector installation procedures. Also, the foil coated inner insulating core may vary in diameter from about .140 inch to as much as about .200 inch.
These small diameter cables have been made available to the consumer in standard lengths with connectors installed at the factory. Also, connectors have been made available for installation, but installation of these connectors to a prepared cable end has typically required a crimping tool for crimping a retaining ferrule, or a tool for spreading a retaining slip ring, or the tighening of a compression nut which retains the connector to the cable end, or the like. Some connectors for indoor service provide and require compressive coaction between the face of the threaded jack and the connector body, which is achieved in practice by tightening a threaded nut of the connector over the outer threads of the jack.
The connectors for indoor service are known as "feedthrough" connectors, in the sense that there is no separate central connector element of the connector provided for connection, the center conductor of the cable providing this element of the connection mechanism. The center conductor is usually engaged by a receptacle element of a jack. Such element, sometimes referred to as a center seizure mechanism, when present, provides a positive mechanical engagement between the connector assembly and the center conductor of the coaxial cable.
In the case of the feedthrough connector, an exposed end portion of the solid wire central conductor of the coaxial cable is directly engaged by the center seizure mechanism of the jack when the feedthrough connector is mounted thereon. Since the central conductor of the coaxial cable is not maintained in mechanical engagement with the feedthrough connectors, and since those connectors function only to feed or connect the outer conductor to the jack and thereby to position the exposed central conductor for engagement with the central gripping mechanism of the jack, the prior techniques for securing the connector to the cable have proven to have drawbacks related to installation and have proven not to be entirely satisfactory for ready installation and extended, reliable use within indoor use environments.
Irrespective of the particular approach followed by the prior art, hitherto there has not been a very low cost feedthrough coaxial cable connector which may be easily assembled and attached to the cable with a simple manipulation by a user without special tools, or skills, and which provides a positive, superior engagement over time with the jack to which it is mated for use.
A wide variety of techniques are to be found in the coaxial cable connector art for attaching a feedthrough connector to a prepared cable end. One representative example is to be found in the Quackenbush U.S. Pat. No. 3,781,762. Therein, a tubular connector body includes an annular flare. The body is dimensioned to fit between the insulating core and outer conductor of the prepared cable end, and it aligns and positions an exposed end section of the central conductor. The annular flare of the tubular body causes the outer conductor to become stretched over it as the body is pushed between the core and the outer conductor during installation. A cylindrical ferrule, such as a split ring or crimp ring, is then installed over the body inside of the annular flare. The Quackenbush arrangement is said to provide good electrical and mechanical connection of the cable outer conductor to the connector body. However, the Quackenbush connector cannot be easily installed on the prepared cable end without special tools needed for installation of the clamping ferrule.
As mentioned, another feedthrough connector relies upon a compression engagement obtained by tightening a threaded nut to the jack. The tightened nut of the connector compresses the outer conductor against the connector body and thereby secures the connector to the cable. One drawback of this approach is that when the nut is not tightened upon the threaded jack, or when the connector end is not engaged with the jack, a slight tug or jerk on the connector may cause it undesirably to become separated from the cable.
Other more conventional approaches are to be found in the coaxial cable connector art which include means for engaging the exposed end of the central conductor. For example, British Patent Specification 621,459 describes a tubular connector body for insertion between the insulation core and the outer conductor of a coaxial cable. An annular flared or bulged region expands the outer conductor of the cable, and a longitudinally extending split ferrule tube is pushed over the coaxial cable end to surround the body at the bulged region so as to press the cable against the bulged region to improve electrical connection and mechanical attachment. The ferrule includes fingers enabling it to be secured to the connector body after it is positioned in place.
An annular split ring is described in the Leeper U.S. Pat. No. 2,805,399 in order to retain an outer conductor of a coaxial cable along a narrow ring location immediately adjacent a bulged annular frustoconical clip portion of a body which is slipped under the outer conductor of the coaxial cable in order to provide very secure mechanical retention of the cable to the connector. Here, a special tool is needed in order to position and install the slip ring.
In the Pugner U.S. Pat. No. 4,053,200, a connector body has two radially raised portions. A plural-fingered, elongated brass ferrule slides over the cable and the outer radially raised portion in order to seat or nest between the two raised portions of the body and press the outer conductor of the cable against the connector body. While the elongated brass ferrule provides a radial band of circumferential compression force to press the cable outer conductor against the tubular body, similar to the manner described in the Quackenbush reference discussed above, no engagement is provided between the elongated ferrule or other structure of the connector and the cable behind the outer raised portion of the connector body. Apparently, to aid requisite securement of the cable to the connector, the Pugner reference teaches a central connector structure which is crimped or otherwise secured to an exposed end section of the central conductor of the cable.
Without the further retention means by the central connector structure as shown in the Pugner patent, tugging and pulling stresses upon the coaxial cable will tend to cause it to become disconnected from the connector as described by Pugner, especially if the connector is threaded onto the jack at the time. Also, any flexures of the cable, particularly within an indoor environment such as the home, will tend to cause the outer conductor to stretch and possibly to lose effective electrical contact with the ridge of the outer raised portion and/or provide an unwanted signal leakage path at the connector.
The Schwartz U.S. Pat. No. 3,264,602 provides a connector body for a coaxial cable which has a rearwardly tapered, ringed frustoconical surface which is slipped under the outer conductor of the coaxial cable. An outer member snap-locks over the cable in a manner which compresses the outer conductor against the frustoconical surface in order to lock the cable to the connector and to provide a positive electrical connection between the inner surface of the outside conductor of the cable and the facing frustoconical ringed surface of the conductive connector body.
The Lee U.S. Pat. No. 4,789,355 provides a coaxial cable connector plug which has tines or leaves which slide over the threaded end of the jack. An outer annular sleeve may then be pushed forward over the tines in order to compress them against the threaded jack and lock the connector plug against the jack in the manner of a compression collet, even though the plug is not threaded to mate with the threads of the jack.
The Samichisen U.S. Pat. No. 4,834,675 describes what the inventor calls a "snap-n-seal" coaxial cable connector for a prepared end of a coaxial cable. This four-part connector assembly includes a mandrel body 30 which has a ramped contour 39 diverging from the rear end thereof, so that the body 30 may be press fit between the dielectric core and the shielding braid. As seen in FIG. 2B and as best seen in FIG. 4, the ramped contour 39 appears to flatten out and ends at a step inwardly forming a right angle with the flattened region. A plastic compression sleeve 60 is pushed over the body 30 and the cable end. The compression sleeve snap-locks into a metal collar member 20 and is said thereby to lock the cable end to the connector assembly. Since the ramped contour 39 appears to end at a flattened region, the body 30 fails to provide a knife edge for effectively cutting into the braid or aluminum sheet forming the outer conductor of the coaxial cable.
The Ito et al. U.S. Pat. No. 4,249,790 describes a push-on type connector plug for a coaxial cable end. In pertinent part, the connector plug includes a slotted shield casing forming a plurality of resilient fingers which engage the outer cylindrical surface of a connector receptacle as the connector plug is pushed onto the receptacle. The fingers appear to be contoured to cooperate with an outer band structure in order to provide a spring bias force which pushes the fingers against the outer cylindrical surface of the receptacle and thereby provide a good electrical and mechanical push-on, pull-off attachment.
The Morello Jr. U.S. Pat. No. 3,196,382 describes a crimp type coaxial cable connector 12 which includes a mandrel body having an integrally threaded mating cap for mating with a receptor connector 14. The Morello Jr. connector device is not a push-on feedthrough connector.
While the foregoing approaches recognize the problem of providing effective contact and positive mechanical attachment of the prepared cable end and the cable connector, none of the foregoing approaches achieve a simplified, easily installed, positively acting feedthrough coaxial cable connector intended primarily for ready installation by the untrained user or consumer or by the trained technician, and for reliable use typically within an indoor environment over an extended time period.